Apparatus for evaporating and distilling



April 27, 1937. B. Fox ET AL 2,078,377

APPARATUS FOR EVAPORATING AND DISTILLING original Fue@ Dec.- 11, 1931 3 sheets-sheet 1 j. M12.; l

B. FOX ET AL APPARATUS FOR EVAPORATING AND DISTILLING April 27, 1937.

ll, 1931 5 Sheets-Sheet 2 Original Filed Dec.

lApril 27, 1937. B, FOX ET AL 2,078,377

- APPARATUS FOR EVAPORATING AND DISTILLING Original Filed Dec. ll, 1931 3 Sheets-Sheet 3 f F550 M157 ro zA/0 J l fFFEcT EVA/D.

0' 'Lg m? 1.43 MM /zll if@ da ,2974 l? f4 i lsv/zusam A'our 70 A fj@ @/W Patented vApr. 27, 1937.

UNITED STATES Rossum 'I APPARATUS Fon EvAronATrNG AND msTrLLING Benjamin Fox, Wollaston, and Charles E. Ericson, Quincy, Mass., assignors, by mesne assignments, to Buena Vista, Iron Company, a corporation of New Jersey Application December 11, 1931, Serial Nvo. 580,286 Renewed May 4, 1935 7 Claims.

This invention relates to an improved apparatus for evaporating and distilling -water and more particularly to such apparatus for use on board ships and the like where it is necessary to supply the fresh or pure water demands from sea water. Such demands are occasioned by the losses cc-` curring due to the operation of the ships machinery, such as condenser,turbine, boiler, auxiliary engines, and the like, together with the ships human needs, such as drinking water.

Heretofore apparatus of this description' has comprised a plurality of units in the Way of Various-stage evaporators. condensers, feed heaters, separators, distillers, and the like, each con- ,l

and distilling of sea water on boardshps into and upon a single shell container in such a compact and eicient manner that there ensues as a result a considerable saving in costs, anincreased eiiic'iency of operation, and a reduction in the requirements of those two most important factors in ship design-Weight and space.

Other objects and advantages will be apparent from' the following description, 'wherein reference is made to the accompanying drawings illustrating .the preferred embodiment of our invention and wherein similar reference numerals designate similar parts throughout the several views.

Fig. 1 is a plan view of our improved apparatus. Fig. 2 is a side elevation thereof. Fig. 3 is a section taken along the linel 3 3 of Fig. 6 viewed in the direction of the arrows. Fig. 4 is a sectiontaken along the lline 4-4 4 of Fig. 6 viewed in the direction of the arrows.

Fig. 5 i's a front end elevation thereof.

Fig. 6 is a partial and combined section in which the left half is -taken along the Iline 6--6 of Fig. 2, and theright half is taken along the line 6--8 of Fig. 4. Y'

Fig. 7 is a detail section taken along the. line Referring now to the drawings, the numeral Ill designates the container shell which comprises the'cylindrical casing II, the front head I2, and

the rear head I3. v'Ill'his lstructure constitutes the (Cranz-174) tank or container for thevbody of sea water (or other liquid) to be evaporated and distilled, and also acts as-the mounting forthe various units required to accomplish the said evaporation or distillation.

It may be noted in Figs. 3 and 6 that the cylindr'ical casing. |I is divided structurally intotwo halves by the .vertical wall I4. The wall I4 is reinforced by the horizontal Vribsn I5, andby the bulbed vertical ribs I6, and the end vertical ribs I1. The front head I2 is reinforced by the vertical wall I 8,v the vertical ribv I9, and the horizontal ribs 20; while the rear head is similarly reinforced by the members 2|, 22 and 23. The ribs Il of the casing abut facially against the ribs I9 and 22. For increased strength and rigidity stay-bolts 24 extend from side to side horizontally on the centerof the 'casing I I and through bosses 25 on the ribs I5 and the Wall I4-thereof. The stay-bolts 24 are threaded at the center for the nuts 26 and at the ends for the nuts 2l, and the said -nuts are adjusted thereon in such a manner that the stay-bolts 24 act both in tension and in compression. to give rigidity and strength to th`e casing and its central wall I4.

The container shell Ill is lthus divided by the walls |4, I8, and`2| into two compartments or chambers, the left hand one -of which as viewed in Fig. 6 we designate as the first eect evaporator chamber 28;` and the right hand one we designate as the second effect evaporator cham- A ber 23. Further sub-division of these chambers will be hereinafter described.4

Contained within the lower halves of the first effect evaporator chamber 28 and of the second effect evaporator chamber 29 are the rst effect 'heater 30 and the second effect heater 3|, respectively. These heaters 30 and 3| are each integral units and are removably attachedas such to the front head I2. They are practically identical in construction, though of opposite hand,A

' .with the exception ofthe heads 32 and 3 3 which because of piping arrangements are slightly different. Therefore the description of one will apply to the other. The head 33 is provided with a horizontal wall 34 which together4 with the front tube sheet 35 forms the enclosed chambers 36 and 31. An upper nest. of tubes 33 and a lower nest A' of tubes 39 extend from the -fronttube sheet 35 /td the rear tube sheet 40 and are supported int'ermediate the ends by a supporting tube sheet 4I..v

'I'he latter is held in spaced relation to the tube y sheet40 by suitable means, such as the bolts 42. A cover head 43 together with the rear tube sheet 40 forms a chamber 44 with which thevrear ends oi all the tubes communicate. For supporting the heaters 30 and 3| and for convenience in removing for cleaning and repair, the tracks 45 and Q6 are provided on the interior of the casing II. Suitable notches in the rear tube sheet 40 and the supporting tube sheet 4| engage the tracks 45 and 46 to locate the heater in place and to guide it upon removal or replacement. The lower nest of tubes 39 is sloped and has an additional bend downward at the -front end to aid in the discharge of condensates.

Within the chambers 28 and 29 and just above th'e heaters 30 and 3| are the deiiecting bailles 41 and 41' which extend full length of the container shell |0 and are suitably fixed to the casing il. Mounted on the stay-bolts 24 by means of clamp- .ing brackets 48 and angles 49 are the double troughed baiiies 50 and 50. These troughed bafiles 50 and 50- extend full length of the container shell I0 and have their longitudinal edges bent downward, inward, and upward to form troughs open for discharge at their ends. Above the baffles 50 and 50 at each side and xed to the casing I I are the single troughed baies 5| and 5| which also extend full length of the container shell I0 and have their free edge troughed similar to the baffles 50. All the baiiies 41, 41, 50, 50', 5|, and

29 at thetop is the '5|' have 'their free ends supported on angle brackets 52 xed to the inner faces of the heads I2 and-I3.

Within the first effect evaporator chamber 28 at the top is the vapor feed heater chamber 53 formed by the walls 54 and 55 in the casing II, and the mating walls 56 and 51 in the heads I2 and I3. The vapor feedheater chamber 53 communicates with the first eiect evaporator chamber 28 through an orifice 58 in the rear half of the vertical wall 54. Fixed to the outside face of the wall 54 and commanding the orifice 58 is the rst effect vapor separator 59. The first effect vapor separator 59 comprises an open ended rectangular frame 60 having a perforated oor plate 6|,'beneath which is xed a' dished cover 62 having at its lower extremity an orifice in which is fixed a s'yphon drain pipe 63. Within the frame 60 are fixed the nested labyrinthine bailies 64. At a mid position longitudinally the floor wall 55 is depressed to form-a collecting trough 65 which communicates with the exterior of the casing I| through an orifice 66; vvapor feed heater chamber-,'53 is the first effect vapor feed heater 61. I'he heater 61 is an integral unit removably attached to the front head i I2. It comprises the conduit head 68, the tube sheet 69, and the nest o f return tubes 10. 'Ihe conduit head 6 8 by reason of a dividing wall 1| forms together with the tube sheet 69 an inlet chamber12 and an outlet chamber 13.

Within the second effect evaporator chamber stilling condenser chamber 14 formed by the walls 15 and 16 in the casing I I,

and the mating walls 11 and 18 in the heads I2 'and I3.

The ldistilling condenser chamber 14 communicates withV the second eect evaporator chamber 29 through the orifices 19. Fixed to the outside face of the wall 15 and commanding the oriiices118 are the .second eifect vapor separators 80. 'Ihe separators 80 are identical indesign to the separator 59 hereinbefore descrlied and need not be further described other than to enumerate the syphon drain pipes 8|.

l At a mid position longitudinally the iloor wall 16 is depressed to form a trough similar to jthat hereinbefore described for the floor wall 66 and need not be further described.

Contained within the' Contained within the distilling condenser chamber 14 is the distilling condenser 82. The distilling condenser 82 is a unit removably attached to the front and rear heads I2 and I3, respectively.- It comprises the front conduit head 83, the rear cover head 84, the tube sheets 8,5 and 86, the three sets, or nests, of tubes 81, 88, and 89, and the baffles 90 and 9| (Fig. 7). The conduit head 83 by reason of dividing walls 92, 93, and 94 forms together with the tube sheet 85 the four enclosed chambers 95, 96, 91, and 98. The chambers 96 and 91 communicate one with the other by reason of an orifice 99 in the wall 93. The rear cover head 84 by reason of a dividing wall |00 forms together with the tube sheet 86 the two enclosed chambers IOI and |02.

Upon the exterior of the container shell I0 and its attached parts hereinbefore described are various pipe connections and the like which we will now describe. In the front conduit head 83 an orifice |03 communicates the chamber 95 with the pipe |04; while the orifice |05 communicates the chamber 96 with the pipe |06; and the orice |01 communicates the chamber 98 with the pipe connection |08. Mounted upon the upper central part of the front head I2 is a standard type air ejector condenser |09 within which a nest of tubes communicate 'at the right end with the pipe connection |08, and at the left end these tubes communicate with thechamber 12 in the conduit head 68 by means of the orifice ||0. Chamber 13 of the conduit head 68 is communicated with the pipe III by means of the orifice ||2. The pipe III forms a line leading to the throttle valve ||3 mounted upon the float feed regulator ||4 which communicates with the first 'effect evaporator chamber 28 by means of the orifice I5, in the casing I I. The oat feed regulator I I4 communicates with the pipe I I6, thence by means of the pipe I I1 and the orifice I I8 to the first eiect evaporator chamber 28. Communicating with the interior of the air ejector condenser I09; at the bottom is the pipe |I9; at the front is the pipe |20; and at thetop is the pipe |2I. The pipe |2I forms a line leading to the standard type air ejector |22 which communicates with the distilling condenser chamber 14 by .means of the orifice |23. The chamber 12 of the conduit head 68 communicates with the, pipe |24 by a suitable orifice (not shown). The pipe |26 forms a line communicating the orifice 66 with the chamber 36 by a suitable orifice in the head 33.-` The chamber 36 by means of the orice |26 communicates with thepipe |21 which in turn communicates with the vapor feed heater chamber-53 by means of the orifice |28. An oriiice |29 in the lower halfof the rear head I3 communicates the ilrst effect evaporator chamber 28 with the pipe |30 leading to the throttle valve I3| mounted upon the iioat feed regulator |32 which communicates with the second effect evaporator chamber 29 by means of a suitable orifice in the casing II. The float feed regulator |32 communicateswith the pipe |33 leading to an orifice |34 in the casing which orifice com# municates with a perforated pipe |35 within the second effect evaporator chamber 29. Orifice |36 at the bottom of the rear head I3 communicates the pipe |31 with the second effect evaporator chamber. The pipe |38 communicates through an orifice |39 in the head 32 with the chamber 'i The oriiice |42 in the casing I I communicates the 'foV acfas?? a 3 chamber 14 with the pipe |43. The orifice |44 communicates the chamber 14 with the pipe |45.

On each side of the casing Il l,observation Windows |46 are suitably mounted by means of which a view of the interiorv may be obtained. Also on each side of the casingy are provided orifices |41 communicating with the chambers 28 and 29, respectively, for the purpose of mounting Water gauge fittings (not shown).

We will now describe the operation of our improved apparatus for evaporating and distiiling sea water as used on board ships. Water is pumped from the sea chest to the distiiling condenser 82 by way of the pipe |04 and the orifice |03 to the chamber 95 of the front conduit head 83. From the chamber 95 the Water flows rear- Wardly through the tube nest 81 to the chamber |0|, then forwardly through the tube nest 88 to the chamber 96. Here, having .served its function as a cooling agent forV the distiiling condenser 82', a large part of the water is automatically deflected through the orifice |05vto the discharge pipe |08 and thence overboard, while the remainder required for distiiling purposes circulates through the orifice 99 to the chamber 91 and then rearwardly through the lower half of the nest of tubes 89 to the chamber |02 and back through the upper half of the nestv of tubes 89 to the chamber 98. The water here leaves the distiiling condenser 82 by way of the orifice |01 and the pipe connection |08 to enter the air ejector condenser |09 and passing through the tube nest therein emerges through the orifice ||0 to the chamber 12 in the conduit head 68 of the vapor feed heater 61. The Water circulates through the return tubes 10 to the chamber 13, leaving the vapor feed heater 61 by way of the orifice H2, to and through the pipe I and the throttle valve H3, and into the float feed regulator H4. The float feed regulator governs the amountV of water passed onward by the height of the water within the first effect evaporator chamber 28 and is preferably a valve controlled bya float of a type well known to those skilled in the art. The water that passes is led by the pipes I |6 and ||1 to the orifice H8 and thence to the interior of the first effect evaporator chamber 28. In the passage of the water as Just described heat has been accumulated therein from the distiiling condenser 82, the air ejector condenser |09, and the vapor feed heater 61. At the same time exhaust steam from the ships auxiliaries is flowing into and through the pipe |38 te the chamber 36' of the first effect heater 30. The steam flows from the chamber 36' through the upper, tube nest 38 to the chamber 44 and back through the tube nest 39' to the chamber 31', and discharging as condensate through the orifice |40 is piped to the ships drain tank (not shown). The exhaust steam .flowing through the heater 30 is sumcent to vaporize the sea water within the chamber 28. As the vapor rises from the surface thereof it is diverted through circuitous or tortuous paths by means of the baffles 41', 50', and 5|'. The rising vapor as it impinges upon the baffles 50', and 5|' tend to deposit entrained water and this is gathered up by the troughed edges of the baffles and led to the ends thereof where it drops back into the main body of the water away from the area of `vapor activity and thus avoids being carried along by the rising vapor. The vapor thus somewhat dried rises to the top of the chamber 28 and flows through the first effect vapor separator 59 and in passing through the tortuous pathways formed by the labyrinthine baffles 64 it is further dried. The entrained water thus removed settles upon the perforated floor plate 6| and flows through to the dished cover 62 below and thence through the syphon drain pipe 63 to discharge upon the sur- 5 face ofthe main body-of water. The vapor flows from the separator 59 into the vapor feed heater chamber 53 and` flows over and around return tubes 10 thus heating the flowing feed water therein. The condensate formed from the vapor 10 3|. The vapor meanwhile flows outward from 15 the chamber 53 through the orifice |28.to and through the pipe |21, and the orifice |26 into the chamber 36 of the second effect heater 3|. The vapor flows from the chamber 36 through the upper tube nest 38 to the chamber 44 and back 20 through the tube nest 39 to the chamber 31. From the chamber `31 the condensate discharges through the orifice |4| and is led by suitable piping to a standard type flash chamber (not shown) Where the condensate isdischarged to a con- 25 densate pump (not shown) for distribution, and

the flash vapor liberated by the reduction of pressure is drawn into the distiiling condenser ch-amber 14 through the pipe |43 and the orifice |42.

The water in the second effect evaporator cham- 30 ber 29 is drawn by means hereinafter described from the first effect evaporator chamber 28 through the orifice |29, -the pipe |30, and the throttle valve |3|, and into the float feed regulator |32. This regulator |32 is identical in func- 35 tion and design to the regulator |14 hereinbefore described. The water that passes through the regulator |32 is led by the-pipe |33 and the orifice |34 to the perforated pipe |35 within the second effect evaporator chamber 29 at the bottom there- 40 of. This water in the chamber 29 is vaporized by the heat of the vapor from the first effect evaporator flowing through the heater 3| as hereinbefore described. The vapor as it rises from the i main body of water in the chamber 29 is acted 45 upon by the baffles 41, 50, and 5| in a similar manner to that described for the first effect evaporator, and need not be further described. Likewise the action of the second effect vapor separators is identical to that described for the 50 first effect vapor separator'59, and need not be further described. 'I'he vapor flows from the separators 80 into the distiiling condenser chamber '|4 where it mingles' with the flash vapor from the pipe |43 hereinbefore. described. 'Ihese 55 vapors flowing over and around the distiiling condenser tubes 81, 88, and 89 are largely condensed-the condensate being collected and drawn off by way of the orifice |44 and the pipe |45 to a condensate pump for distribution, while 60 the remaining vapor is withdrawn between the baffles 90, and 9| through the orifice |23 tothe air ejector |22. The air ejector |22 is functioned by a steam'jet fed from a connection to the auxiliary steam line (not showniand tends to 65 Icreate a vacuum in the distiiling condenser chamber 14 and in the second effect evaporator chamber 29 thus acting to draw off the remaining vapor as just described and also to establish a pressure differential with respect to the' rst 70 'effect evaporator chamber 28, which results in maintaining the feed water pressure flow as hereinbefore described and in low pressure evaporation in the second effect evaporator chamber 29.

The air ejector |22 discharges byway of the pipe 75 |2| into the air e'J'ector condenser |09, where, in a manner well known to the art, the non-condens'- ing vapors are exhausted to the atmosphere through the pipe |20 and the condensate is discharged to the ships draintank through the pipe H9. An emergency discharge line pipe |24 with a cut-o valve l 24 is provided whereby feed water from the chamber 12 of the rst effect vapor 'feed heater 61 may be discharged overboard. A brine discharge line pipe |31 is connected to the 'orifice |36 whereby water in the second effect evaporator chamber 29 that has become surcharged with salt may be pumped overboard and replaced by the normal feed water as hereinbefore described.

It will now be apparent that we have devised a novel apparatus for evaporating and distilling, especially applicable to marine purposes but it will be manifest that it is useful and valuable for application to other elds. It will be readily seen from the above description that we have devised a novel heat exchange apparatus whereby the surface areas subject to heat radiation losses are reduced to a minimum by placing condensers, distillers, heaters, and the like Within a single container. We have made a considerable saving in the cost and weight of individual containers and piping required; all of which makes for general compactness of design with its consequent saving in space and Weight-thus complying with the most valuable desideratum in the ship building art.

It is also apparent that the container shell lli could be of other shape than a's shown and described without departing from the spirit of our invention, but We have shown it in our preferred form as being substantially cylindrical and horizontal. In this form it combines practically with a maximum of container volume and structural strength for a minimum requirement of space and weight.

Although we have described and illustrated our invention in considerable detail, we do not Wish to be limited to the exact and specic de- -tails thereof as shown and described, but may use such modification in, substitution for or equivalent thereof, as are embraced within the scope of our invention or as pointed out in the claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In an apparatus for evaporating and distilling, a horizontal cylindrical container shell, said container shell being divided into two substantially equal compartments by an integral vertical longitudinal wall member, said wall being strengthened by integral vertical and horizontal transverse ribs and by a plurality of staybolts xed to said wall and to opposed sides of said container shell normal to said Wall and to said opposed sides, one of said compartments having a vaporizing portion adapted to contain a heating unit and the liquid to be vaporized, a Vapor drying portion adapted to contain vapor drying units, and a vapor condensing portion adapted to contain a vapor condenser unit, the said vaporizing portion together with the said Vapor drying portion and the condensing portion being inter-communicating, the other of said compartments having a vaporizing portion adapted to contain a heating'unit and the liquid to be vaporized, a vapor drying portion adapted to contain vapor drying units, and a distilling condenser portion adapted to contain adistilling condenser unit, the second mentioned vaporizing portion together with the second mentioned vapor drying portion and the said distilling condenser portion being inter-communicating, vacuum and vacuum condenser means mounted upon the said container shell in communication With the said distilling condenser portion of the second of said compartments, separate float feed regulator means mounted exteriorlyof the first and second mentioned compartments in connection With each of the said vaporizing portions, piping means connected in series to the distilling condenser unit, to the vacuum condenser means, to the vapor condenser unit, to the feed regulator means of the iirst mentioned compartment, and to the rst mentioned vaporizing portion, piping means connecting the vapor condensing portion to the second mentioned heating unit, piping means vconnected in series to the first mentioned vaporizing portion, to the second compartment float feed regulator, and to the second mentioned vaporizing portion, pure water drain piping means communicating with the vacuum condenser, with the rst mentioned heating unit,

with the second mentioned heating unit, and

with the distilling condenser unit, and undistilled Water drain piping `means communicating With the vapor condensing unit, with the distilling condenser unit, and with the second mentioned vaporizing portion.

2. In an apparatus for evaporating and distilling, a container shell comprising a plurality of compartments, one of said compartments adapted to automatically receive the liquid to be evaporated and distilled and to contain a heater means to heat and vaporize said liquid, baffles and separator meansA adapted to collect condensate and return it to the body of said liquid and vapor condenser means adapted to dry`said vapor and collect the condensate, and a second of said compartments adapted to automatically receive liquid from the iirst compartment and to contain a heater means heated by the dried vapor from the rst compartment, bailies and separator means adapted to collect condensate from the vapor rising in the secondfcompartment and return it to the body of the liquid, and distilling condenser means to collect the condensate from the latter vapor, air ejector and condenser means mounted upon said container shell to draw non-condensable vapor from the second compartment and to condense and-collect the condensate thereof, and piping means mounted on the shell container to carry the condensate from the first compartment vapor condenser to the second compartment heater piping, to carry the liquid to the rst compartment through the circulating tubes of the distilling condenser, the air ejector condenser, and the vapor condenser before entering the said automatic feed means, and to collect and distribute the condensate from the distilling and air ejector condensers.

3. In an apparatus for evaporating and distilling, a container shell containing a plurality of primary compartments, one of said primary compartments being divided into separate inter-communicating vaporizing and condensing compartments, another of said primary compartments being divided into separate inter-communicating F vaporizing and distilling compartments, heating units contained within said vaporizing compartments and condensing units contained within said condensing and distilling compartments, piping connecting in series the feed water system to the said condensing units and to the first men-v tioned primary compartment, piping connecting the said condensing compartment of the first mentioned primary compartment tol the heating unit of the second mentioned primary compartment, feed water piping connecting the Vaporizing compartment of the first mentioned primary compartment to the vaporizing compartment of the second mentioned primary compartment, and vacuum means mounted on the container shell and connected to said distilling compartment whereby a pressure differential is maintained between the first mentioned primary compartment and the second mentioned primary compartment.

4. A multiple effect evaporating and distilling apparatus, comprising a first compartment and a second .compartment within a single container, each of said compartments being adapted to contain a body'of liquid separated by acommon wall, each of said compartments having a liquid vaporizing portion and a vapor condensing portion, heater means within said rst compartment for heating and vaporizing liquid therein, means for conveying feed liquid in preheat heat interchanging relationship successively with vapor in the vapor condensating portion of said second compartment and the vapor condensating portion of said first compartment whereby said vapors in )both compartments are condensed while preheating said feed liquid, means for conveying feed liquid thus preheated into the liquid .vaporizing portion of said first compartment, means for conveying heated liquid from said first compartment into saidsecond compartment, means for conveying Vapor from said first compartment into heat interchanging relationship with the liquid in said second compartment for vaporizing liquid therein, means for collecting for use condensates formed in both said first and said secon-d compartments, and vacuum inducing means in communication with the vapor condensing portion of said second compartment whereby a vapor pressure differential is maintained between said first compartment and said second compartment.

5. A multiple effect evaporating and distilling apparatus,` comprising a iirst compartment and a second compartment within a single container, each of said compartments being adapted to contain a body of liquid separated by a common wall, each of said compartments having 'a liquid vaporizing portion and a vapor condensing portion, heater means Within said first compartment for heating and vaporizing liquid therein, means for conveying feed liquid in preheat heat interchanging relationship successively with vapor in the vapor condensating portion of said second compartment and the vapor condensating portion of said first compartment whereby said vapors in both compartments are condensed while preheating said feed liquid, means for conveying feed liquid thus preheated into the liquid vaporizing portion of said first compartment, means for conveying heated liquid from said first compartment into said second compartment, means for conveying vapor from said first compartment into heat interchanging relationship with the liquid in said second compartment for vaporizing liquid therein, means for collecting for use condensate formed in the vapor condensing portion of said second 'veying heated liquid compartment, andvacuum inducingv means in communication with the vapor condensing portion of said second compartment vwhereby a-vapor pressure differential is maintained between said first compartment and said second compartment.'

6. A multiple leffect-evaporating and distilling apparatus, comprising a first compartmentand a second compartment within a singlefcontainer, each of said compartments being adapted to con'- tain a body of liquid separated by a common wall, each of said compartments having a liquid vaporizing portion and a vapor condensing portion, heater means within said first compartment for heating a-ndyaporizing-'liquid therein, means for conveying feed liquid in preheat heat interchanging relationship successively with vapor in the -vapor 'condensating portion of said second ,compartment and the vapor condensating portion of said first compartment whereby said vapors in both compartments are condensed while preheating said feed liquid, means for conveying feed liquid thus preheated into the liquid vaporizing portion of said first compartment, means for confrom said first compartment into said second compartment, means for conveying vapor from said first compartment into heat interchanging relationship with the liquid in said second compartment for vaporizing liquid therein, means for collecting condensate formed in the vapor condensing portion of said first compartment and conveying it to said means for conveying vapor to said second compartment, means for collecting for use the condensate formed in the vapor condensing portion of said second compartment, and vacuum inducing means in communication with the vapor condensing portion of said second compartment whereby a vapor pressure differential is maintained between said first compartment and saidV heating and vaporizing liquid therein, means for conveying feed liquid in preheat heat interchanging relationship successively with vapor in the vapor condensating portion of said second lcom--l vpartment and the vapor condensating portion of said first compartment whereby said vapors in vboth compartments are condensed while preheating said feed liquid, means for conveying feed liquid thus preheated into the liquid vaporizing portion of said first compartment, means for conveying heated liquid from said first compartment into said second compartment; means for Vconveying vapor from said first compartment into heat interchanging relationship with the liquid in said second compartment for vaporizing liquid therein,

means for collecting for use condensate formed in the vapor condensing portion of said second compartment, and means for maintaining a vapor pressure differential between the two compart.

ments.

BENJAMIN FOX. CHARLESv E. ERICSON. 

